System and a method for controlling a centrifuge for the production of a skimmed milk product

ABSTRACT

The present disclosure includes a method of controlling a centrifuge for the centrifugal production of a milk product. The steps include taking a milk sample at an outlet of the centrifuge from a liquid phase, adding a substance to the milk sample that increases light transmittance of the milk sample, determining the light transmittance of the milk sample by transilluminating the milk sample using a light source and measuring light intensity via a photo cell, determining the fat content from a measurement of the light transmittance, and controlling the centrifuge as a function of the determination of the fat content. The present disclosure also includes a system for controlling the centrifuge.

CROSS-REFERENCE

This application claims priority to German Application 101 35 073.2filed Jul. 18, 2001, which disclosure is hereby incorporated herein byreference.

BACKGROUND AND SUMMARY

The present disclosure relates to a method of controlling and/orregulating a centrifuge for the centrifugal production of a milkproduct. It also relates to a system for implementing the method.

It is known to, for example, separate milk into skimmed milk and creamby centrifuges. Disk separators are generally used for this purpose.

During the separation into skimmed milk and cream, it is a goal of thecentrifugal separation to minimize the fat content in the skimmed milkas much as possible in order to design the economical yield of themethod to be as optimal as possible.

Unfortunately, the determination of the fat content of cream or skimmedmilk is relatively problematic since the skimmed milk or the cream havea white coloring, so that methods for determining the lighttransmittance of the skimmed milk are high-expenditure (laboratory)processes, such as the process by Röse-Gottlieb and the process byMojonier with precisions or a reproducibility of 0.03% and 0.015%.

The present disclosure provides for a method of controlling and/orregulating a centrifuge for the centrifugal production of a milk productas well as a system for implementing the method. The controlling and/orregulating of the centrifuge is simplified and a determination of thefat content becomes possible which is as precise as possible, and issimpler in comparison to the known laboratory processes and isindependent of the latter.

Thus, the present disclosure relates to a method of controlling acentrifuge for the centrifugal production of a milk product. The methodsteps comprise: taking a milk sample at an outlet of the centrifuge froma liquid phase; adding a substance to the milk sample that increaseslight transmittance of the milk sample; determining the lighttransmittance of the milk sample by transilluminating the milk sampleusing a light source and measuring light intensity via a photo cell;determining fat content of the milk sample from a measurement of thelight transmittance; and controlling the centrifuge as a function of thedetermination of the fat content.

The liquid phase from which the mild sample is taken may be skimmedmilk. Furthermore, it should be noted that, by adding the substance,such as a suitable alkaline solution, to the milk sample, the pH-valueis increased. It then becomes possible in a simple manner to increasethe light transmittance of the white milk sample to such an extent thatsurprisingly it is possible to use an optical method for determining thefat content. The determination of the fat content can be carried out inintervals by a computer in an automated manner. If the computer, inturn, is connected with the control inputs of the actual centrifugecontrol, or the computer is even used for controlling the centrifuge, itbecomes possible to utilize the information not only for monitoring thesetting of the centrifuge but also for its controlling and/or also forthe regulating as a function of the determination of the fat content.However, a manual monitoring by a person reading a display unit can alsobe implemented.

The light transmittance of the liquid phase, particularly of the skimmedmilk, is increased in that the substance increasing the pH-value isproportioned and added such that the pH-value of the milk sample isincreased to 11–14, preferably 12–13, and particularly to 13.

The present disclosure also relates to a system for controlling acentrifuge for the centrifugal production of a milk product. The systemincludes a device that takes a milk sample from a liquid phase at anoutlet of the centrifuge. Also included is a device that adds asubstance to the milk sample that increases light transmittance of themilk sample. Further included is a device that determines the lighttransmittance of the milk sample and from which a fat content of themilk sample is determinable. With regard to the system, it can beconstructed, for example, as a separate unit and assigned to orconnected with the centrifuge. Further, a device for controlling and/orregulating the setting of the centrifuge as a function of the determinedfat content may be preferably assigned to or connected with the devicefor determining the light transmittance.

Other aspects of the present disclosure will become apparent from thefollowing descriptions when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system for controlling a centrifuge,according to the present disclosure.

FIG. 2 is a diagram illustrating the testing of reproducibility ofselected test results, according to the present disclosure.

FIG. 3 is a diagram illustrating a ratio of the fat content to displayvalue of the photo cell, according to the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a centrifuge constructed as a disk separator 13 whichhas an inlet 12 for milk product 28 as well as an outlet 14 for creamand an outlet 1 for skimmed milk and skimmed whey. After centrifugalseparation of the inflowing milk product 28 into cream and skimmed milk,it is possible to take skimmed milk from the outlet 1 of the centrifugeby way of a sample-taking pipe 2 connected into the outlet 1 of thecentrifuge 13 and to guide this skimmed milk into a first storage tank3. The removal takes place in front of a regulating or constant-pressurevalve 23 assigned to or connected behind the centrifuge 13 in order totake the skimmed milk sample from a largely foam-free area.

A valve 4 is connected in front of the storage tank 3 and, when thefirst storage tank 3 is being filled, is opened until skimmed milk exitsby way of a vent pipe 5 which is assigned to or connected with the firststorage tank 3 and leads into collecting vessel 22. The size of thefirst storage tank 3 determines a volume which is required or used formeasurements.

Another valve 9 for letting off the skimmed milk sample from the firststorage tank 3 is connected behind the first storage tank 3. The valve 9at the outlet of the first storage tank 3 is connected by way of a line16 with a measuring cell 24 which may be an optical measuring cell, andwhich includes a sample-taking vessel 25, a light source 26 and a photocell 27. The measuring cell 24 is connected with an analyzing and/ordisplay device 11 (such as a computer, which also controls themeasurements).

In addition, from a second storage tank 18, a liquid L or othersubstance (not shown) for increasing the pH-value of the milk sampledischarged from the first storage tank 3 is connected in front of themeasuring cell 24. From the second storage tank 18, the liquid Lincreasing the pH-value or the other substance increasing the pH-value,can be guided by way of an automatic valve 6 into a third storage tank7. Again, the size of the third storage tank 7 determines the requiredvolume. The third storage tank 7 is filled when liquid exits from anoverflow bore or pipe 8 which is assigned to the third storage tank 7and leads into the collecting vessel 22.

As soon as the two storage tanks 7 and 3 have been filled, the valves 9and 10 connected behind the two storage tanks 7 and 3 are opened. Thishas the result that the liquids contained in the storage tanks 3 and 7flow by way of the valves 9 and 10 into the sample-taking vessel 25 andare mixed there. By the addition of the liquid or substance from thethird storage tank 7, the pH-value of the skimmed milk is increased suchthat the structure of protein situated in the skimmed milk is alteredsuch that a light transmittance of the milk sample is achieved.

A quantitative proportion from the storage tanks 3 and 7 may be 2:3,when a suitable alkaline solution is used as the liquid or substance forincreasing the pH-value.

From the previously-mentioned light transmittance, a residual fatcontent can now be determined. For this purpose, the light transmittanceis determined, which takes place by irradiating the milk sample by thelight source 26 and the photo cell 27 arranged relative to the lightsource 26 behind the measuring cell 24.

Empirically, a corresponding table can be determined which indicates thedependence of the light transmittance on the residual fat content. Thetable can then be stored in a computer, so that, after the measuring ofthe light transmittance of the milk sample, the cloudiness and thus thefat content are determined by a comparison with the stored table. By acorresponding adjustment, it is even conceivable to provide theanalyzing and/or display device 11 directly with a scale which indicatesthe residual fat content when a display is implemented which isproportional to the light transmittance. In this manner, the analysis ofthe determination of the fat content is further simplified. FIG. 3,which illustrates that the measurements are independent of thetemperature and indicates the proportionality between the photo cell 27display and the residual fat content, demonstrates that this display canbe implemented.

Weak, almost crystal-clear skimmed milk samples have, for example, aresidual content of approximately 0.05% fat. In contrast, considerablecloudiness indicates a residual fat content of approximately 0.15%.

After the measurement of the light transmittance, the milk sample isdischarged from the measuring cell 24, for example, by way of a valve20, into the collecting vessel 22.

Using the measurement, a setting of the centrifuge can be changed in theevent of deviations from a desired value either manually orautomatically, for example, by a computer (not shown here) connected tothe measuring cell 24 and the disk centrifuge 13.

FIG. 2 shows that a reproducibility can be achieved within a range of1/1,000. This precision permits the usage of the present measuringmethod for controlling and/or regulating separators. In the case of adeterioration of the skimming value, a complete evacuation or a CIP(cleaning in place), for example, can be carried out. A reproducibilityof less than 0.005% may possibly even be realistic.

Although the present disclosure has been described and illustrated indetail, it is to be clearly understood that this is done by way ofillustration and example only and is not to be taken by way oflimitation. The scope of the present disclosure is to be limited only bythe terms of the appended claims.

1. A method of controlling a centrifuge for the centrifugal productionof a skimmed milk product, the steps comprising: taking a skimmed milksample at an outlet of the centrifuge from a liquid phase; adding asubstance to the skimmed milk sample that increases light transmittanceof the skimmed milk sample; determining the light transmittance of theskimmed milk sample by transilluminating the skimmed milk sample using alight source and measuring light intensity via a photo cell; determiningthe fat content of the skimmed milk sample from a measurement of thelight transmittance, the determining being done in an automated mannerat intervals using a computer; providing a centrifuge control deviceconnected to the centrifuge; and controlling the centrifuge, using thecontrol device, as a function of the determination of the fat contentwhile the light transmittance of the skimmed milk sample is determined.2. The method according to claim 1, wherein the light transmittance ofthe skimmed milk sample is increased by the substance increasing thepH-value of the skimmed milk sample.
 3. The method according to claim 2,wherein the pH-value is proportioned and added such that the pH-value ofthe skimmed milk sample is increased to 11–14.
 4. The method accordingto claim 2, wherein the pH-value is proportioned and added such that thepH-value of the skimmed milk sample is increased to 12–13.
 5. The methodaccording to claim 2, wherein the pH-value is proportioned and addedsuch that the pH-value of the skimmed milk sample is increased to
 13. 6.A system for controlling a centrifuge for the centrifugal production ofa skimmed milk product, comprising: a first device configured to take askimmed milk sample from a liquid phase at an outlet of the centrifuge,the first device including a sample-taking pipe and a first storagetank; a second device configured to add a substance to the skimmed milksample that increases light transmittance of the skimmed milk sample,the second device including a second storage tank and a valve; a thirddevice configured to determine the light transmittance of the skimmedmilk sample and from which a fat content of the skimmed milk sample isdeterminable, the third device including a measuring cell including asample-taking vessel, a light source, and a photocell, and the thirddevice using a computer to determine the fat content of the skimmed milksample at intervals in an automated manner; and a fourth deviceincluding a control device configured to be connected to control thecentrifuge as a function of the determined fat content.
 7. The systemaccording to claim 6, wherein the fourth device is connected with thethird device configured to determine the light transmittance.
 8. Thesystem according to claim 6, further including a first valve leadinginto the first storage tank, the sample-taking pipe and first valvebeing connected with the outlet of the centrifuge.
 9. The systemaccording to claim 6, wherein the sample-taking pipe is connected infront of a constant pressure valve.
 10. The system according to claim 6,wherein the first storage tank is connected via a second valve with themeasuring cell.
 11. The system of claim 10, wherein at least one of ananalyzing device and a display device is connected with the measuringcell.
 12. The system according to claim 6, wherein the second storagetank is configured to receive a substance for increasing the pH-value ofthe skimmed milk sample and is connected in front of the measuring cell.13. The system according to claim 6, wherein at least one of ananalyzing device and a display device is connected with the measuringcell.
 14. The system according to claim 13, wherein the at least one ofthe analyzing device and the display device is provided with a scalewhich directly displays a residual fat content of the skimmed milksample.
 15. The system according to claim 6, wherein the system is aseparate measuring unit which is connected with the centrifuge.
 16. Thesystem of claim 6, wherein the centrifuge is a disk separator.
 17. Thesystem of claim 6, wherein the measuring cell includes an opticalmeasuring cell.